According to a well-known method for cleaning surfaces of power generating equipment, these surfaces are washed with an aqueous solution of a preset composition. Prior to washing, the surfaces are purged with steam.
Purging with steam is done for mechanical removal of loose deposits. Iron oxides, which firmly adhere to the surface of power generating equipment, are removed by washing that surface with aqueous solution of a mixture of Trilon B and citric acid. The final step of the process is the passivation of the metal with sodium nitrite or some other corrosion inhibitor (cf. "Chimicheskiye ochistki teploenergeticheskogo oborudovaniya"/"Chemical Cleaning of Heat-Power Equipment"/, Issue 2 ed. by T. Margulova, Energia Publishers, Moscow, 1978, pp. 6, 31). The method is disadvantageous in that it necessitates the use of short-supply and expensive products and purification of effluents. It also involves extensive preparatory work even with the fullest possible utilization of the available power generating equipment.
There is further known a method for chemical cleaning of internal heat surfaces of power generating equipment, which consists in filling the inside of power generating equipment with moist steam fed at a speed of 6 to 8 m/sec. The steam is maintained at a temperature of 150.degree. C. and has a water content of about 5 percent. Concentrated solution of ammonium salt of ethylene diamine tetraacetic acid (200 to 250 g/l) is added to the moist steam at a rate of 1.5 ton per hour. Also added to the moist steam is a mixture of corrosion inhibitors (the concentration of each is 200 g/l), which is fed at a rate of 0.25 ton per hour (cf. the journal "Energomachinostroyeniye"/"Power Plant Engineering"/, No. 1, 1980, pp. 42-45). The treatment is carried out for 7 hours with a high concentration of the detergent in the moist steam, which amounts to about 200 g/kg. It is followed by purging the equipment with superheated steam, which is carried out over a brief period of time. The method is disadvantageous in that even with a low content of water in the steam the distribution of water inside the equipment being cleaned is not uniform enough, wherefore the removal of deposits is not complete. In addition, the method necessitates the use of short-supply and costly chemical products, as well as the use of special equipment for the purification of effluents.
There is known a method for cleaning internal heat surfaces of power generating equipment according to USSR Inventor's Certificate No. 651,189 of 1972, Cl. F 28 G 13/00. This method consists in washing internal heat surfaces of power generating equipment with aqueous acid solutions and simultaneously filling and heating the inside of the equipment with steam having a temperature of 300.degree. C. to 500.degree. C. The inside of the equipment is then filled with oxygen and washed again with aqueous acid solutions.
The method is too complicated, because a complete removal of deposits from internal heat surfaces of power generating equipment requires multiple cleaning with the use of chemically aggressive reagents. The method according to the above-mentioned USSR Inventor's Certificate involves two cleaning cycles with the use of aqueous solution of hydrochloric acid. Cleaning pipes by filling and heating them with superheated steam and then filling them with oxygen is not effective enough. It takes much time, to say nothing of the fact that it requires additional equipment, including effluent purification installations.